The present invention relates to a water pump bearing to be used for a water-cooled engine of an automobile or the like.
Referring to FIG. 6, in a conventional water pump for a water-cooled engine of an automobile or the like, an impeller is attached to an end portion of a pump shaft 53 and a pulley 52 is attached to the other end portion thereof respectively, so that the pulley 52 causes the impeller 51 to rotate, to thereby circulate cooling water. For fixing such a water pump, as shown in FIG. 6, generally a water pump bearing is press-fixed in a water pump housing 50 fixed to a main body of the engine. With the water pump bearing, the pump shaft 53 provided with the impeller 51 at an end portion thereof and the pulley 52 at the other end portion thereof respectively is rotatably attached to an outer ring 54 of the bearing with a rolling member 55 located therebetween.
Between the outer ring 54 and the pump shaft 53, a mechanical seal 57 is provided for sealing a space 58 between the pump housing 50 and the pump shaft 53 to isolate from the impeller 51.
Also, seal structures are respectively provided at the end portions of the outer ring 54, for sealing a space therewithin. Among the seal structures, a seal structure 56 on the impeller side is generally constituted of a metal ring reinforcement and an elastic member reinforced by the ring reinforcement.
In such water pump in the public domain, when sealing effect of the mechanical seal 57 is deteriorated because of chronological transition etc., cooling water may penetrate from the impeller 51 side of the seal 57 into the space 58 between the pump housing 50 and the pump shaft 53.
In addition, the seal structure 56 on the impeller side is repeatedly heated and cooled each time the engine is started and stopped, causing repeated expansion and contraction of air inside the bearing, for which the sealing effect is prone to be damaged.
Accordingly, the cooling water that has penetrated into the space 58 between the pump housing 50 and the pump shaft 53 in the above described manner, or vapor generated from heating the cooling water may penetrate into the internal area of the bearing through the seal structure 56.
Such penetration of moisture into the internal area of the bearing causes a breakdown of the water pump because of deterioration of grease filled inside the bearing or rust produced inside the bearing, shortening a life span of the water pump.
Moreover, the grease may flow out of the internal area of the bearing through the seal structure 56, at which the sealing effect of it has been deteriorated by the aforementioned reasons. The outflow of the grease increases friction between the rolling member 55 and the pump shaft 53, which leads to a breakdown of the water pump bearing, and consequently to a shorter life span of the water pump.
In view of the foregoing problems with the prior art, it is an object of the present invention to provide a water pump bearing that can prevent penetration of cooling water or moisture into an internal area of the water pump bearing, and outflow of grease from the internal area of the bearing.
For achieving the object, a water pump bearing according to the invention is constituted as follows.
The water pump bearing comprises, like conventional ones, a pump shaft provided with an impeller at one end portion thereof and a pulley at the other end portion thereof respectively, rotatably attached to an outer ring of the bearing with at least one rolling member located therebetween, and seal structures provided at both end portions of the outer ring for sealing an internal area of the bearing.
Also, there is a seal structure on a side of the impeller, among the seal structures provided at both end portions of the outer ring for sealing the internal area of the bearing, comprises the following characteristic constitution.
The seal structure of a first embodiment comprises a ring-shaped first seal unit having an outer circumferential portion fixed to an inner circumferential portion of the outer ring and an inner circumferential portion in sliding-contact with an outer circumferential surface of the pump shaft. As shown in FIG. 1, in the seal structure of the first embodiment, a ring-shaped second seal unit is disposed at an axially outer position from the first seal unit. And, the second seal unit has its inner circumferential portion fixed to an outer circumferential portion of the pump shaft and its outer circumferential portion in sliding-contact with the outer ring.
The first seal unit comprises a ring reinforcement and an elastic member reinforced by the ring reinforcement. An outer circumferential portion of the first seal unit is press-fitted in a fitting groove formed on an inner circumferential surface of the outer ring. A portion of the elastic member further extends from an end portion of the ring reinforcement on the pump shaft side toward the pump shaft for making sliding-contact with an outer circumferential surface of the pump shaft. That portion of the elastic member comprises a first lip portion extending diagonally in an axially inward direction to make sliding-contact with an outer circumferential surface of the pump shaft, and a second lip portion extending diagonally in an axially outward direction to make sliding-contact with an outer circumferential surface of the pump shaft.
The second unit comprises a ring reinforcement having a cylindrical portion extending in an axial direction and fixed to the pump shaft and a flange portion extending from the cylindrical portion toward the outer ring, and an elastic member reinforced by the ring reinforcement. A portion of that elastic member further extends from the outer ring side end portion of the flange portion of the ring reinforcement toward the outer ring comprises a third lip portion in sliding-contact with an axially outer end face of the outer ring.
In the seal structure of a second embodiment, as shown in FIG. 2, a portion of the elastic member which constitutes the second seal unit is like the first seal structure, but a portion of that elastic member further extends from the outer ring side end portion of the flange portion of the ring reinforcement toward the outer ring further comprises a fourth lip portion extending diagonally in an axially inward direction to form a non-contact labyrinth seal portion between an axially outer lateral face of the first seal unit.
In the seal structure of a third embodiment, as shown in FIG. 3, a ring reinforcement and an elastic member which constitute the second seal unit are like those of the first seal structure or the second seal structure, but a cylindrical portion of a ring reinforcement further has a reinforcing ring extending from the cylindrical portion toward radially inner direction along an axially outer end face of the pump shaft, and a portion of an elastic member existing at the side of radially inner part of it and reinforced by the said reinforcing ring comprises a fifth lip portion in sliding-contact with the axially outer end face of the pump shaft.
In the seal structure of the fourth embodiment, as shown in FIG. 4, the second seal unit is like the first embodiment of a seal structure. It comprises a ring reinforcement and an elastic member reinforced by the ring reinforcement. The inner circumferential portion of the second seal unit is press-fitted in a fitting groove formed on an outer circumferential surface of the pump shaft. A portion of the elastic member further extends from the outer ring side end portion of the ring reinforcement toward the outer ring so as to form a third lip portion in sliding-contact with an axially outer end face of the outer ring.
In the seal structure of the fifth embodiment, as shown in FIG. 5, a portion of the elastic member constituting the second seal unit is like the fourth seal structure, but a portion of that elastic member further extends from the outer ring side end portion of the ring reinforcement toward the outer ring further comprises a portion extending diagonally in an axially inward direction to form a fourth lip portion that serves as a non-contact labyrinth seal portion between an axially outer lateral face of the first seal unit.
In a water pump bearing of the invention comprising a seal structure of any of the first to fifth aspects on the impeller side, as one of the seal structures provided at both end portions of the outer ring for sealing an internal area of the bearing, the third lip portion of the second seal unit can make sliding-contact with the axially outer end face of the outer ring that has a plain, e.g. a planar surface. It is also possible to provide an arc-shaped chamfer portion at an inner circumferential corner (on the pump shaft side) of the axially outer end face of the outer ring, so that the third lip portion makes sliding-contact with the arc-shaped chamfer portion.
According to the water pump bearing of the invention, the seal structure on the impeller side of the seal structures provided at both end portions of the outer ring for sealing the internal area of the bearing is comprised as follows. The structure comprises the ring-shaped first seal unit having its outer circumferential portion fixed to an inner circumferential portion of the outer ring and its inner circumferential portion in sliding-contact with an outer circumferential surface of the pump shaft, and the ring-shaped second seal unit disposed at an axially outer position from the first seal unit with its inner circumferential portion fixed to an outer circumferential portion of the pump shaft and its outer circumferential portion in sliding-contact with the outer ring. Therefore, penetration of moisture, such as cooling water or vapor etc., into the internal area of the bearing can be effectively prevented, and outflow of grease from the internal area of the bearing can also be effectively prevented.
More specifically, even if moisture, such as water or vapor, etc., has penetrated toward the internal area of the bearing through the seal portion between the third lip portion of the second seal unit and the axially outer end face of the outer ring, the second lip portion of the first seal unit, which diagonally extends in an axially outward direction and achieves sliding-contact with an outer circumferential surface of the pump shaft, prevents moisture, such as water or vapor, etc., from penetrating into the internal area of the bearing.
Also, the first lip portion of the first seal unit, which diagonally extends in an axially inward direction and achieves sliding-contact with the outer circumferential surface of the pump shaft, prevents grease from outflowing from the internal area of the bearing.
Further, in both of the foregoing cases, a sealed space enclosed by the first lip portion and the second lip portion of the first seal unit and the outer circumferential surface of the pump shaft can effectively prevent penetration of moisture, such as cooling water or vapor, etc., into the internal area of the bearing, as well as preventing outflow of grease from the internal area of the bearing.
Also, where the second unit further comprises the fourth lip portion that extends diagonally toward the outer ring and in an axially inward direction to form a non-contact labyrinth seal portion between an axially outer lateral face of the first seal unit, even if moisture, such as water or vapor, etc., has penetrated toward the internal area of the bearing through the seal portion between the third lip portion of the second unit and the axially outer end face of the outer ring, the labyrinth seal portion shakes off such moisture, thus effectively preventing further penetration of moisture, such as water, or vapor, etc., into the area of the bearing.
In any of the seal structures adopted in the water pump bearing of the invention, it is preferable that the ring reinforcements be made of a corrosion-resistant material, for example stainless steel, to avoid generation of rust on these components. In this sense the material is not specifically limited as long as these components are made of a corrosion-resistant material. For example, steel plated with a corrosion-resistant metal may be employed.
Also, elastic members may be of materials known in this technical field, such as rubber or synthetic resin.
Also, constitution, configuration and arrangement described in the following preferred embodiments referring to the accompanying drawings are merely a general presentation for reasonable understanding of the invention. Therefore, it is to be understood that the invention is not limited to the forms disclosed in the following embodiments, and that various modifications and variations may be made within the technical scope of the invention as set forth in the appended claims.